Gas sensors are widely used across many diverse applications including commercial, industrial, military and other applications. The sensitivity of such gas sensors can vary, and the type of gas sensor used for a particular application is often selected depending on the required sensitivity and cost. In some applications, it may be desirable to detect gas concentrations as low as a few parts per billion, or even less. Many commercially available gas sensor, such as cavity ring down gas sensors, provide an optical cavity having an internal beam of light that is pumped up to a relatively high beam intensity in order to increase the sensitivity of the sensor. Monitoring and controlling the beam intensity can have implications on the operation of such sensors.